Allocating resources for a device-to-device transmission

ABSTRACT

A method for allocating resources for device-to-device transmission between two or more user equipment (UEs) includes transmitting, from a first UE to a second UE, a resource allocation configuration for device-to-device communications. A resource request for a device-to-device transmission is received from the second UE. In response to the resource request, a resource for the device-to-device transmission is selected at the first UE. A resource grant is transmitted to the second UE. The resource grant identifies the selected resource. A device-to-device transmission is received from the second UE over the selected resource.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityU.S. patent application Ser. No. 15/948,439, filed on Apr. 9, 2018,which claims priority to U.S. patent application Ser. No. 14/712,779,filed on May 14, 2015 and issued as U.S. Pat. No. 9,942,917 on Apr. 10,2018, the entire contents of which are hereby expressly incorporated byreference herein in their entireties.

TECHNICAL FIELD

This disclosure relates to data transmission in wireless communicationsystems and, more specifically, to allocating resources fordevice-to-device transmissions.

BACKGROUND

In a device-to-device (D2D) communication, a user equipment may transmitto another user equipment directly using an enhanced cellular radioaccess technology. Examples of the cellular radio access technology thatcan be enhanced for D2D communications include Global System for Mobilecommunication (GSM), Interim Standard 95 (IS-95), Universal MobileTelecommunications System (UMTS), CDMA2000 (Code Division MultipleAccess), Evolved Universal Mobile Telecommunications System (UMTS), LongTerm Evaluation (LTE), LTE-Advanced, any other cellular technology or awireless broadband access technology, such as Wi-Fi technology. In oneexample, a user equipment may transmit directly to another userequipment in a D2D communication using the LTE radio access technology.

DESCRIPTION OF DRAWINGS

FIG. 1 is an example wireless communication system that allocatesresources for device-to-device (D2D) transmissions.

FIG. 2 is a flowchart illustrating an example process for allocatingresources in an autonomous selection mode.

FIG. 3 is a flowchart illustrating an example process for allocatingresources in a network scheduled mode.

FIG. 4 is a message flow diagram illustrating an example process fortransmitting a resource allocation configuration.

FIG. 5 is a message flow diagram illustrating another example processfor transmitting a resource allocation configuration.

FIG. 6 is a flowchart diagram illustrating an example resource selectionprocess.

FIG. 7 is a flowchart illustrating an example frequency-first resourceselection process.

FIG. 8 is a message flow diagram illustrating an example resourceallocation process for a user equipment (UE) that operates in anautonomous selection mode.

FIG. 9 is a message flow diagram illustrating an example resourceallocation process for a UE that operates in a network scheduled mode.

FIG. 10 is a message flow diagram illustrating an example extendedperiod process for a remote UE operating in an autonomous selectionmode.

FIG. 11 is a message flow diagram illustrating an example extendedperiod process for a relay UE operating in an autonomous selection modeand scheduling resource allocation for remote UEs.

FIG. 12 is a message flow diagram illustrating an example extendedperiod process for a relay UE operating in a network scheduled mode andscheduling resource allocation for remote UEs.

FIG. 13 is a message flow diagram illustrating an example schedulingrequest (SR) transmission process for a relay UE operating in anautonomous selection mode.

FIG. 14 is a message flow diagram illustrating an example SRtransmission process for a relay UE operating in a network scheduledmode.

FIG. 15 is a flowchart illustrating an example method for allocatingresources for D2D transmissions.

FIG. 16 is a flowchart illustrating another example method forallocating resources for D2D transmissions.

FIG. 17 is a flowchart illustrating an example method for transmitting ascheduling request.

FIG. 18 is a block diagram illustrating an example user equipment (UE)device.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The present disclosure is directed to allocating resources fordevice-to-device (D2D) transmissions in a system capable of D2Dcommunications. D2D communications can be used to provide commercialservices, e.g., a Mission Critical Push-To-Talk (MCPTT) service. TheMCPTT service supports an enhanced Push-To-Talk (PTT) service that canbe used for professional groups, e.g., public safety departments,transport companies, utilities, industrial plants, or nuclear plants, ornon-professional groups, e.g., groups of people on holiday. In somecases, the MCPTT service supports group calls among several users, aswell as private calls between a pair of users. In some cases, the MCPTTservice may use The Third Generation Partnership Project (3GPP)transport communication mechanisms provided by the Evolved Packet System(EPS) architectures to establish, maintain, and terminate the actualcommunication paths among the users. In some cases, the MCPTT servicemay use non-3GPP, e.g., dispatcher or administer, access technologiesand architectures.

In some cases, the communications between the users in a group in theMCPTT service may be implemented using D2D transmissions. For example,in some cases, a UE may be in a location that is out of the coverage ofa cellular network. Such a UE may be referred to as a remote UE. In somecases, such a UE may be referred to as a second UE. In these or othercases, the remote UE may use D2D transmissions to communicate withanother UE in the same MCPTT group. For example, the remote UE may use aD2D transmission to send a data packet to a relay UE that is in thecoverage of the network. The relay UE can relay the data packet to thenetwork, which forwards the data packet to other UEs in the MCPTT group.Similarly, the relay UE can relay the data packets received from thenetwork to the remote UE in a D2D transmission. In some cases, the D2Dtransmission can be referred to as a Proximity-based Service (ProSe). Insome cases, the D2D transmission can be referred to as a directcommunication. In some cases, the interface between corresponding UEs ina D2D transmission can be referred to as a PC5 interface. In some cases,the transmission link between corresponding UEs in a D2D transmissioncan be referred to as a sidelink transmission link, which can bedistinguished from an uplink (UE to base station) or from a downlink(base station to UE) transmission link. In some cases, the relay UE canbe referred to as a UE-to-Network Relay (UNR). In some or other cases,the relay UE may be in a location that is out of the coverage of acellular network and may use D2D transmissions to relay informationbetween other UEs. In these or other cases, the relay UE can be referredto as a UE-to-UE Relay (UUR). In some cases, the relay UE may bereferred to as a first UE.

In some cases, the resource for a D2D transmission may include resourcesthat a UE can use to transmit control information, data packets, or acombination thereof. As discussed herein, “resource” or “resources” mayeach include indifferently a single resource or multiple resources. Forexample, the resource can include Physical Sidelink Control Channel(PSCCH) resources for the transmission of Sidelink Control Information(SCI). The resource can also include Physical Sidelink Shared Channel(PSSCH) resources for the transmission of sidelink data packets. In somecases, the SCI may be used to indicate scheduling information to theProSe receiving UEs. The ProSe receiving UE may use the SCI to identifythe sidelink resources that are used to transmit data on the PSSCH.

In some cases, a UE may be in a network scheduled mode or in anautonomous selection mode. In some cases, the network scheduled mode maybe referred to as a network scheduled allocation mode or as Mode 1. Insome cases, the autonomous selection mode may be referred to as anautonomous resource selection mode or as Mode 2. If a UE is in a networkscheduled mode, the UE may request the resource from a base station.Alternatively, if a UE is in an autonomous selection mode, the UE mayselect the resource from one or more resource pools. The one or moreresource pools may be signaled by the base station using a broadcastmessage or a dedicated message. Alternatively or in combination, the oneor more resource pools may be preconfigured at the UE. As discussedherein, “pool” or “pools” may each include indifferently a single poolor multiple pools. In some case, a base station may use a broadcast or adedicated message to indicate which mode should be used by the UEs inthe coverage of the base station.

In some cases, a base station may specify a particular mode, e.g.,either a network scheduled mode or an autonomous selection mode, for theUEs in the coverage of the base station. In some cases, for example,when a UE that is out of a coverage of a base station, the UE may not beable to request resources from the base station. Therefore, the UE maynot use the network scheduled mode, and the UE may use autonomousselection mode instead. Because a UE in the autonomous selection modedoes not coordinate with other UEs or the base station in selectingresources, the resources selected by the UE may collide with resourcesselected by other UEs operating in the autonomous selection mode, orresources assigned by the base station to a UE operating in the networkscheduled mode. The possibilities of collisions increase as the numberof remote UEs that are in proximity to one another increases. Acollision of resources may result in failures for the D2D transmissionsand, therefore, delay or prevent the successful delivery of data packetsbetween the UEs.

In some cases, in order to reduce the effects of the resource collisionand associated transmission failure, a UE may repeat the data packettransmissions for multiple times. Such repetition may be inefficientbecause it increases the resources used to transmit the same packet andsometimes still does not avoid collisions. In some cases, this approachmay cause a traffic peak and consequently further increase thecollisions. In some cases, the resource pools may be overprovisioned toreduce the possibilities of collisions. Alternatively, different poolsmay be configured for different UEs. However, because the total amountof resources available for D2D transmissions may be limited, theseapproaches may not be practical if there are a large amount of UEs thatuse D2D transmissions.

FIG. 1 is an example wireless communication system 100 that allocatesresources for D2D transmissions. For example, a resource allocationconfiguration may be transmitted from a first UE to a second UE fordevice-to-device communications. The resource allocation configurationmay be determined by at least one of the base station and the first UE.In some cases, some of the resource allocation configuration informationmay be pre-configured at the first or the second UE. In some cases, thefirst UE may operate in an autonomous selection mode. A resource requestfor a device-to-device transmission may be received from the second UE.In response to the resource request, a resource for the device-to-devicetransmission may be selected at the first UE. A resource grant may betransmitted to the second UE. The resource grant may identify theselected resource. A device-to-device transmission may be received fromthe second UE over the selected resource.

In some implementations, a resource allocation configuration may betransmitted from a first UE to a second UE for device-to-devicecommunications. In some cases, the first UE may operate in a networkscheduled mode. A resource request for a device-to-device transmissionmay be received from the second UE. A sidelink resource request may betransmitted to a base station in response to the resource request. Inresponse to the sidelink resource request, a sidelink allocationinformation may be received. The sidelink allocation information mayidentify the resource for the device-to-device transmission. A resourcegrant may be transmitted to the second UE. The resource grant mayidentify the selected resource. A device-to-device transmission isreceived from the second UE over the selected resource.

In some implementations, a sidelink control information may be receivedat a relay UE from a remote UE. The relay UE may be within a coveragearea of a base station. The coverage area of the base station may be acoverage area providing access to a PLMN service in which the second UEis interested. The PLMN service may be a MCPTT service. The remote UEmay be outside of the coverage area. The relay UE may be configured torelay transmissions from the remote UE to the base station. The sidelinkcontrol information may indicate a future transmission of a data packetover a sidelink channel. A scheduling request may be transmitted to abase station. In some cases, the scheduling request may be transmittedto the base station before a start of the future transmission of thedata packet. In some cases, the data packet may be transmitted in morethan one redundancy version, and the scheduling request for uplinktransmission may be transmitted to the base station in response toreceiving one or more redundancy versions of the data packet or an SCIin PSCCH. In some cases, the scheduling request may be transmitted tothe base station after at least one data packet is decoded at the relayUE. A scheduling grant that indicates an uplink resource may be receivedfrom the base station. A data packet over the sidelink channel may bereceived from the remote UE. The data packet may be transmitted to thebase station using the uplink resource.

Allocating resources for D2D transmissions according to methods andsystems described herein may provide one or more advantages. Forexample, a relay UE may schedule resources for a remote UE and selectthe resources that may minimize collisions with other resources. In somecases, a UE may coordinate the resource selections with other UEs tofurther minimize collisions. In some cases, the base station may alsoavoid or reduce substantially scheduling transmissions that may overlapwith D2D transmissions by considering the resource configuration usedfor D2D transmissions. In addition, signaling overhead for allocatingresources and coordinating may be reduced by extending the resourceallocation period. In some cases, signaling overhead may be furtherreduced by preconfiguring a subset of resource pools in a UE.

At a high level, the example wireless communication system 100 includesa wireless communication network 110, which includes a base station 106that is configured to communicate with a first UE 102. In some cases,the connecting interface between the first UE 102 and the base station106 may be referred to as a Uu interface. In the illustrated example,the first UE 102 is communicatively coupled with a second UE 104. Thefirst and the second UEs communicate using D2D transmissions over asidelink 120. In the illustrated example, the first UE 102 is within thecoverage area of the base station 106 and the second UE 104 is outsideof the coverage area of the base station 106. In some cases, the firstUE 102 may serve as a relay UE to relay data packets received from thesecond UE 104 to the base station 106, and to relay data packetsreceived from the base station 106 to the second UE 104. In some cases,both the first and the second UEs may be within the coverage area of thebase station 106, or within the coverage areas of different basestations. In some cases, one base station may provide a service that thesecond UE wishes to receive and one other base station may not. In somecases, both the first and the second UEs may be outside the coverageareas of any base stations in the wireless network 110.

In some cases, the first UE 102 operates in an autonomous selectionmode. A resource allocation configuration for device-to-devicecommunications is transmitted from the first UE 102 to the second UE104. A resource request for a device-to-device transmission is receivedfrom the second UE 104. In response to the resource request, a resourcefor the device-to-device transmission is selected at the first UE 102. Aresource grant is transmitted to the second UE 104. The resource grantidentifies the selected resource. A device-to-device transmission isreceived from the second UE 104 over the selected resource. FIG. 2-18and associated descriptions provide additional details for theseimplementations.

In some cases, the first UE 102 operates in a network scheduled mode. Aresource request for a device-to-device transmission is received fromthe second UE 104. A sidelink resource request is transmitted to thebase station 106 in response to the resource request. In response to thesidelink resource request, a sidelink allocation information isreceived. The sidelink allocation information identifies the resourcescheduled for the device-to-device transmission. A resource grant istransmitted to the second UE 104. The resource grant identifies thescheduled resource. A device-to-device transmission is received from thesecond UE 104 over the scheduled resource. FIG. 2-18 and associateddescriptions provide additional details for these implementations.

Turning to a general description of the elements, a UE may be referredto as mobile electronic device, user device, mobile station, subscriberstation, portable electronic device, mobile communications device,wireless modem, or wireless terminal. Examples of a UE (e.g., the firstUE 102 or the second UE 104) may include a cellular phone, personal dataassistant (PDA), smart phone, laptop, tablet personal computer (PC),pager, portable computer, portable gaming device, wearable electronicdevice, or other mobile communications device having components forcommunicating voice or data via a wireless communication network. Thewireless communication network may include a wireless link over at leastone of a licensed spectrum and an unlicensed spectrum.

Other examples of a UE include mobile and fixed electronic device. A UEmay include a Mobile Equipment (ME) device and a removable memorymodule, such as a Universal Integrated Circuit Card (UICC) that includesa Subscriber Identity Module (SIM) application, a Universal SubscriberIdentity Module (USIM) application, or a Removable User Identity Module(R-UIM) application. The term “UE” can also refer to any hardware orsoftware component that can terminate a communication session for auser. In addition, the terms “user equipment,” “UE,” “user equipmentdevice,” “user agent,” “UA,” “user device,” and “mobile device” can beused synonymously herein.

The wireless communication network 110 may include one or a plurality ofradio access networks (RANs), core networks (CNs), and externalnetworks. The RANs may comprise one or more radio access technologies.In some implementations, the radio access technologies may be GlobalSystem for Mobile communication (GSM), Interim Standard 95 (IS-95),Universal Mobile Telecommunications System (UMTS), CDMA2000 (CodeDivision Multiple Access), Evolved Universal Mobile TelecommunicationsSystem (UMTS), Long Term Evaluation (LTE), or LTE-Advanced. In someinstances, the core networks may be evolved packet cores (EPCs).

A RAN is part of a wireless telecommunication system which implements aradio access technology, such as UMTS, CDMA2000, 3GPP LTE, and 3GPPLTE-A. In many applications, a RAN includes at least one base station106. A base station 106 may be a radio base station that may control allor at least some radio-related functions in a fixed part of the system.The base station 106 may provide radio interface within their coveragearea or a cell for a UE to communicate. The base station 106 may bedistributed throughout the cellular network to provide a wide area ofcoverage. The base station 106 directly communicates to one or aplurality of UEs, other base stations, and one or more core networknodes.

While elements of FIG. 1 are shown as including various component parts,portions, or modules that implement the various features andfunctionality, nevertheless these elements may instead include a numberof sub-modules, third-party services, components, libraries, and such,as appropriate. Furthermore, the features and functionality of variouscomponents can be combined into fewer components as appropriate.

FIG. 2 is a flowchart illustrating an example process 200 implementing atechnique for scheduling resources allocation for remote UEs by a UEoperating in an autonomous selection mode. This technique may also bereferred to as a remote resource allocation, a remote sidelink resourceallocation or a remote D2D resource allocation. The process 200 maybegin at block 202, where a first UE operates in an autonomous selectionmode. In some cases, the first UE may be a relay UE. In some cases, thefirst UE may be a UE-to-Network Relay or a UE-to-UE Relay. In somecases, the first UE may be a remote UE. In some implementations, asdescribed in more detail below, the first UE may select the radioresources for the D2D transmissions of other UEs.

At block 204, the first UE signals a resource allocation configurationto other UEs. The resource allocation configuration may be determined byat least one of the base station and the first UE or may consist inpre-configured information within at least one of the first and thesecond UEs. In some cases, a resource allocation configuration mayindicate a remote resource allocation capability. The remote resourceallocation capability may instruct or enable other UEs to request D2Dresources from the first UE. In some cases, the resource allocationconfiguration may include information of resource pool for sidelinktransmissions. FIG. 4 and associated descriptions provide additionaldetails according to an example implementation.

At block 206, the first UE receives a resource request for adevice-to-device transmission from a second UE. In some cases, thesecond UE may be a remote UE. In some cases, the second UE may be a UEthat is within a network coverage, and therefore, is not able or notconfigured to receive a service from the network. In some cases, anassigned sidelink resource is valid in a Sidelink Control (SC) period.In these or other cases, the second UE may send a request for each SCperiod. The request may be sent before the start of a SC period forwhich the resource is requested, and the second UE may allocate theresource for the SC period.

In some cases, the request may include Quality of Service (QoS)information. Examples of QoS information may include QoS ClassIdentifier (QCI), Guaranteed Bit Rate (GBR), Maximum Bit Rate (MBR), orpriority. The QoS information may be used by the first UE to determinethe type of resources that the second UE is requesting. For example, theQCI may be set to a value that represents a voice service, a dataservice, or a combination thereof.

In some cases, the request may also include information about the amountof data to be transmitted. For example, the request may include a BufferStatus Report (BSR) that indicates the buffer size for the data to betransmitted. In some cases, the request may include resourcecategorization information, e.g., the duration of the resource, the sizeof the resource, etc.

The following is an example of the resource request message for asidelink resource.

ResourceAllocationRequest Message

-- ASN1START ResourceAllocationRequest ::= SEQUENCE {  groupId-r13INTEGER (0 . . 63),  qCI-r13 INTEGER (0 . . 255),  priority-r13 INTEGER(1 . . 16),  lCG-ID-r13 INTEGER (0 . . 3),  bufferSize-r13 INTEGER (0 .. 63) OPTIONAL } -- ASN1STOP ResourceAllocationRequest fielddescriptions groupid Indicates the identifier of the group for whichsidelink resources are requested. qCI Indicates the QCI associated tothe direct communication session for which sidelink resources arerequested. ICG-ID Identifies the group of logical channel(s) for whichsidelink resources are requested. Should be set to “11” in this versionof the specification. bufferSize Provides information about the amountof data to be sent per LCG or per UE.

At block 208, the first UE selects a resource for the D2D transmission.In some cases, the first UE may select the resource to minimizecollisions with other assigned resources. FIG. 6-8 and associateddescriptions provide additional details according to an exampleimplementation.

At block 210, the first UE transmits a resource grant to the second UE.The resource grant can be used by the second UE to identify the resourcefor the D2D transmission.

In some cases, the second UE may use the following two types ofinformation to identify the resources: description of a pool ofresources and scheduling information.

In some cases, a pool of resources for D2D transmissions may beconfigured by a base station. The first UE may transmit the descriptionof the pool of resources to the second UE before the start of an SCperiod. In some cases, the first UE may transmit the description of thepool of resources to the second UE as a resource allocationconfiguration. In some cases, as described before, the description ofthe pool of resources may be included in the resource allocationconfiguration at block 204. In one example, the description may betransmitted to the second UE as part of relay information or relaystatus over a Sidelink Discovery CHannel (SL-DCH), a Physical SidelinkDownlink Discovery CHannel (PSDCH) or another sidelink channel during arelay discovery or the relay selection procedure. In another example,the description may be transmitted to the second UE in a systeminformation block broadcast message over a Sidelink Broadcast CHannel(SL-BCH) or a Physical Sidelink Broadcast CHannel (PSBCH). In somecases, the description may be transmitted in a MasterInformationBlockfor Sidelink (MB-SL) message, an extension of the MIB-SL, or a newmessage, e.g., a SystemInfomrationBlock1 (SIB1) like message forSidelink. In yet another example, the description may be transmitted tothe second UE in a point-to-point sidelink signaling message, e.g., aResource Pool Information message, over a Sidelink Shared CHannel(SL-SCH), a Physical Sidelink Shared CHannel (PSSCH) or another sidelinkchannel.

In some cases, a base station may update the configuration of the poolof ProSe resources. In these or other cases, the first UE may send anupdated description to the second UE.

In some cases, a resource pool description can include at least one ofan SC period, a Cyclic Prefix length for control and data, Time andFrequency parameters, e.g., subframe bitmap for time resource patternand resource block pattern, synchronization parameters, power controlinformation, or TDD operation parameter, if applicable.

In some cases, different information elements may be used to indicatedifferent types of resource pools. For example, commTxPoolNormalCommonmay be used to indicate a common resource pool, which is used in normalconditions. CommTxPoolExceptional may be used to indicate a pool ofresource used in exceptional conditions. Examples of exceptionalconditions include physical layer problems or radio link failure. Insome cases, the UE may use the resource pool indicated by thecommTxPoolExceptional when operating in network scheduled mode.CommTxPoolNormalDedicated may be used to indicate a pool of resourcesused during Radio Resource Control (RRC)_CONNECTED state if configuredby the network. In some cases, this pool may be signaled inRRCConnectionReconfiguration by the network when autonomous selectionmode is configured.

In some cases, a “finger-printing” mechanism, e.g., mark-up, timestamp,hash-code, or other references, can be used to identify a particularconfiguration of the pool of ProSe resources. For example, a referencenumber may be associated with the current pool. The reference number maybe broadcast in the MIB-SL. A UE may compare the reference number of thepreviously acquired pool information with the broadcasted referencenumber. The UE may request updated pool information if the number isdifferent. This approach may reduce the resources used to transmit thedescriptions when the pool has not been changed. In some cases, atimestamp may be used in conjunction with the reference number to avoidusing outdated pool configuration.

In some cases, the description may need to be updated if changed by thenetwork during the communication session (an update of the MIB-SL or ofthe Resource Pool Information message may be sent by the relay).

In some cases, the scheduling information or resource grant may includea frequency hopping flag, a resource blocks assignment for data, a timeresource pattern used for data, a Modulation and Coding Scheme (MCS)used for data, a Timing Advance Indication, a Group Destination Id, or acombination thereof. In some cases, the scheduling information may betransmitted using an SCI format 0 or an enhanced SCI format.

In some cases, the scheduling information may be transmitted to thesecond UE in a sidelink signaling message over PC5, e.g., a ResourceAllocation Grant message.

The following is an example of the resource grant message for a sidelinkresource.

ResourceAllocationGrant Message

-- ASN1START ResourceAllocationGrant ::= SEQUENCE { sCI-resource-index-r13 INTEGER (0 . . 31),  tPC-command-r13 INTEGER (0. . 1),  frequencyHopping-r13 INTEGER (0 . . 1),  resourceBlockAss-r13INTEGER (1 . . 8192),  tRP-index-r13 INTEGER (0 . . 127) } -- ASN1STOPResourceAllocationRequest field descriptions sCI-resource-indexIndicates the index to determine the SCI frames for PSCCH transmission.tPC-command Indicates the power control command. frequencyHoppingIdentifies whether frequency hopping shall be used or not.resourceBlockAss Provides the resource block assignment for the SCperiod. tRP-index Provides the Time Resource Pattern index for the SCperiod (FDD).

At block 212, whether a communication session has ended is determined.In some cases, the scheduling information is valid for an SC period.Therefore, if the session does not end, the process 200 proceeds toblock 206, where a new request may be received by the first UE for a newSC period. The process 200 repeats until the communication session ends.

FIG. 3 is a flowchart illustrating an example process 300 implementing atechnique for scheduling resources allocation for remote UEs by a UEoperating in a network scheduled mode. This technique may also bereferred to as a remote resource allocation, a remote sidelink resourceallocation or a remote D2D resource allocation. The process 300 maybegin at block 302, where a first UE operates in a network scheduledmode. In some cases, the first UE may be a relay UE that relays D2Dtransmissions from other UEs to a base station.

At block 304, the first UE signals a resource allocation configurationto other UEs. In some cases, a resource allocation configuration mayindicate a remote resource allocation capability. The remote resourceallocation capability may instruct or enable other UEs to request D2Dresources from the first UE. In some cases, the resource allocationconfiguration may include information that describes the resource poolfor sidelink transmissions. FIG. 4 and associated descriptions provideadditional details according to an example implementation.

At block 306, the first UE receives a resource request for one or moredevice-to-device transmissions from a second UE. In some cases, thesecond UE may be a remote UE. In some cases, the second UE may be a UEthat is within a network coverage.

At block 308, the first UE requests and obtains a resource for the D2Dtransmissions. In some cases, the first UE requests and obtains theresource from a base station. FIG. 9 and associated descriptions provideadditional details according to an example implementation.

At block 310, the first UE transmits a resource grant to the second UE.The resource grant can be used by the second UE to identify the resourcefor the D2D transmissions. In some cases, the second UE may use thefollowing two types of information to determine the resources:description of a pool of resources and scheduling information. In somecases, the first UE may forward the description of pool information andthe scheduling information received from the base station to the secondUE. In some cases, the first UE may forward the description of poolinformation to the second UE as a resource allocation configuration.

At block 312, whether a communication session has ended is determined.In some cases, the scheduling information is valid for an SC period.Therefore, if the session does not end, the process 300 proceeds toblock 306, where a new request may be received by the first UE for a newSC period. The process 300 repeats until the communication session ends.

FIG. 4 is a message flow diagram illustrating an example process 400 fortransmitting a resource allocation configuration. As discussedpreviously, in some cases, the first UE can transmit a resourceallocation configuration to indicate a remote sidelink resourceallocation capability. In some cases, the capability can be transmittedas relay information or relay status over a sidelink channel during arelay discovery or relay selection procedure or in an MIB-SL broadcastby the relay UE over PSBCH. In some cases, the MIB-SL may be transmittedperiodically, e.g., with a 40 milliseconds periodicity.

In some cases, the first UE may determine whether to turn on theresource allocation techniques described in FIG. 2-3 and associateddescriptions. The first UE may set the remote sidelink resourceallocation capability indicator to “1” if the first UE determines to usethe technique. Alternatively or in combination, the first UE may set thecapability indicator to “0.” If the capability indicator is set to “0,”other UEs may not request sidelink resources from the first UE. Instead,other UEs may select the resources by themselves if operating in theautonomous selection mode, or request resources from a base station ifoperating in the network scheduled mode.

In some cases, the first UE may determine whether to turn on theresource allocation technique described in FIG. 2-3 and associateddescriptions, depending on the mode, e.g., the autonomous selection modeor the network scheduled mode, that the first UE operates in. In somecases, the first UE may signal to the second UE the mode, e.g., theautonomous selection mode or the network scheduled mode, that the firstUE operates in and the capability of any resource allocation techniquedescribed in FIG. 2-3 and associated descriptions, and the second UE maydetermine whether to use or not the corresponding resource allocationtechnique (e.g. depending on transmission latency requirements).

In some cases, the resource allocation configuration signaling may beomitted. For example, the support for the remote resource allocationtechnique may be mandatory for a relay UE. Therefore, a remote UE mayrequest resources from a relay UE without receiving the resourceallocation configuration.

Referring to FIG. 4 , the process 400 begins at 402, where the relay UEbroadcasts an indication on the PSBCH to signal the support of resourceallocation to remote UEs. At 404, the relay UE repeats the indication in40 milliseconds. At 406, the remote UE 1 and the relay UE initiateresource allocation for sidelink transmissions.

FIG. 5 is a message flow diagram illustrating another example process500 to signal the support by the relay UE of resource allocation toremote UEs. The process 500 begins at 502, where the relay UE transmitsthe resource allocation configuration to a remote UE over a PSCCH. Theresource allocation configuration indicates that the relay UE supportssidelink resource allocation. Alternatively or in combination, theresource allocation configuration can be transmitted over a PSSCH. Insome cases, the resource allocation configuration may be transmitted ina one-to-one transmission between the relay UE and the remote UE.Alternatively or in combination, the resource allocation configurationmay be transmitted in a one-to-many transmission between the relay UEand multiple remote UEs. At 504, the remote UE and the relay UE initiateresource allocation for sidelink transmissions.

FIG. 6 is a flowchart diagram illustrating an example resource selectionprocess 600. The process 600 may begin at 602, where the first UEdetermines that a resource needs to be selected. The determination maybe triggered by a resource request from a second UE as describedpreviously.

At 604, the first UE may select a resource from a pool of resources forthe sidelink transmission. The resource may include an SCI resource forthe SCI transmission and the time and frequency resources for thesidelink data transmission. As discussed previously, in some cases, thepool of resources may be configured by the base station. Alternativelyor in combination, the pool of resources may be pre-configured at thefirst UE, the second UE, or a combination thereof. The pool of resourcesmay include an SCI resource pool for SCI transmission and a dataresource pool for sidelink data transmission.

In some cases, the first UE may select orthogonal (non-colliding)resources with other assigned sidelink resources. In some cases, otherassigned sidelink resources may include resources assigned by the firstUE for sidelink transmissions from the first UE, resources assigned bythe first UE for sidelink transmissions from one or more second UEs, orresources assigned by other UEs that the first UE is aware of. Forexample, the first UE may exclude the SCI resource already selected forthe considered SC period and randomly select an SCI transmissionresource from the not yet selected SCI resources in the SCI resourcepool.

In the illustrated example, the first UE may determine the timingresource information for the sidelink data transmission before thefrequency resource information. In some cases, the timing resourceinformation may include a load value parameter, K_(TRP) for a timeresource pattern (TRP). K_(TRP) represents a number of allocatedsubframes within a configured number of subframes. In one example, theconfigured number of subframes may be 8. In this or other examples,K_(TRP) may be set to 1, 2, or 4 subframes, indicating that 1, 2, or 4subframes within the 8 subframes are allocated to a particular sidelinktransmission. In some cases, the first UE determines K_(TRP) based onthe QoS information received in the resource request, based on asubframe bitmap associated to the resource pool, or based on acombination thereof. For example, if the second UE indicates in the QoSinformation that a high data rate service or a high buffer size isassociated with the request, the first UE may set K_(TRP) to a highnumber.

The timing information may include a TRP, which may be a bitmap thatindicates the subframes of the allocated resource. For example,“10101010” is a TRP, which represents the first, third, fifth, andseventh subframes in an 8-subframe subset. In some cases, the first UEmay select the TRP so that it has minimum overlap with TRPs that areassigned to other sidelink transmissions in the SC period. In somecases, the TRP can be represented as TRP, which may be an index to theTRP. For example, I_(TRP) may be set to 56 to indicate the “10101010”TRP.

In some cases, the first UE may select the resource to minimizecollisions with other assigned resources. For example, the first UE mayselect a TRP based on a collision distance between this TRP and thealready assigned TRPs. The first UE may calculate the hamming distancesbetween the candidate TRPs for the second UE transmissions from aconfigured pool of sidelink resources and any other assigned TRP for theconsidered SC period. The first UE may select among the candidate TRPsthe TRP that has a highest hamming distance with any other assigned TRP.

At 606, the first UE may select a frequency resource for the sidelinkdata transmission. In some cases, the first UE may select the resourceblocks (RBs) that have minimum collision with RBs that are assigned toother sidelink transmissions in the SC period for the subframes includedthe selected time resource pattern. At 608, the first UE marks theselected resources in both time domain and frequency domain. Thisapproach helps the first UE to keep track of the selected resources andminimize collisions in allocating resources for other sidelinktransmissions.

At 610, the first UE indicate the assigned resource, i.e. transmits theresource grant, to the second UE. FIG. 8 and associated descriptionsprovide additional details of these implementations.

In some cases, the first UE may determine the frequency resource for thesidelink data transmission before the time resource. FIG. 7 is aflowchart illustrating an example frequency-first resource selectionprocess 700. The process 700 may begin at 702, where the first UEdetermines that a resource needs to be selected. At 704, the first UEmay select a resource for the sidelink transmission. As discussedpreviously, the first UE may exclude the SCI resource already selectedby the relay for the same SC period and randomly select an SCItransmission resource from the remaining SCI resource pool.

In the illustrated example, the first UE also determines the frequencyresource information for the sidelink data transmission before the timeresource information. The first UE may determine the number of RBs basedon the QoS information received in the resource request, based on amodulation and coding scheme to be used, or a combination thereof. Forexample, if the second UE indicates in the QoS information that a highdata rate service or a high buffer size is associated with the request,the first UE may determine a high number of RBs. The first UE may alsoselect RBs that have minimum collision with RBs that are assigned toother sidelink transmissions in the same SC period.

At 706, the first UE may select a time resource for the sidelink datatransmission. As discussed previously, the first UE may determineK_(TRP) based on the QoS information received in the resource request.The first UE may also select an I_(TRP) such that the corresponding timeresource pattern has a minimum collision distance with other assignedtime resource patterns. At 708, the first UE marks the selectedresources in both time domain and frequency domain to keep track of theselected resources. At 710, the first UE transmits the resourceinformation to the second UE. FIG. 8 and associated descriptions provideadditional details of these implementations.

In some cases, e.g., when the first UE is a relay UE operating in theautonomous selection mode, the first UE may also coordinate the sidelinkresources selection with other relay UEs in the vicinity which arelikely to interfere on its allocated sidelink resources. The other UEsmay operate in either the autonomous selection mode or the networkscheduled mode. Such coordination may be based on communicating sidelinkresource scheduling information (e.g., at least one of frequencyresources or time patterns) between these relay UEs, either throughsidelink transmission or through the cellular network. This may enablerelay UEs in proximity to avoid selecting the colliding resources.

In some cases, the coordination between the relay UEs may be used incombination with extended sidelink resource allocation as discussed inFIG. 10-12 . This approach may reduce overhead for the coordination.

To coordinate the sidelink resource allocation, the relay UEs mayexchange the identification of the resource pool(s) used by the relay,the description of the pool, the description of the sidelink resourceselected by the relay UE, or a combination thereof.

In some cases, the coordination information may be exchanged using atleast one of a broadcast, a multicast or a point-to-point transmissionbetween relay UEs over a PC5 interface. In some cases, the cellularnetwork may store and forward the coordination information to the relayUEs. For example, the cellular network may forward the identity of therelay UEs and the pool information associated to each relay UEs.

In some cases, a relay UE may notify a target relay UE or the cellularnetwork for sidelink resource usage information. In some cases, a targetrelay UE may be another relay UE that is in proximity with the relay UE.The relay UE may include relevant pool information as described above.The target relay UE or the network may store the request and the relayUE identity. The target relay UE or the network may reply to or informthe relay UE with the relevant pool information used by the target relayUE.

In some cases, the relay UE may signal the sidelink resource allocationinformation to target relay UEs. In some cases, the sidelink resourcesinformation may be communicated before the start of each SC period or anextended resource allocation period as discussed in FIG. 10-12 . In somecases, the sidelink resource information may be transmitted directlyover the PC5 interface instead of through a network path to avoidadditional delays.

In some cases, a relay UE receiving information about resource usage bytarget relay UEs may take this information into account for allocatingsidelink resources. For example, the relay UE may avoid using theseresources when selecting resources for sidelink transmissions.

In some cases, instead of receiving the resource usages by target relayUEs over PC5 interface or through a network, the relay UE may decode thePSCCH of neighboring sidelink transmitters and obtain the usageinformation.

FIG. 8 is a message flow diagram illustrating an example resourceallocation process 800 for a UE that operates in autonomous selectionmode according to the technique described in FIG. 2 and associateddescription. As illustrated, process 800 may begin at step 1, where thefirst UE receives configuration information for a resource pool from thebase station. At step 2, the first UE may be selected as a relay UEserving the second UE and indicates that it supports resource allocationaccording to the designated technique. At step 3, the second UE sends aresource allocation request. At step 4, the first UE selects a resource.At step 5, the first UE sends a resource allocation grant to the secondUE. The resource allocation grant indicates the resource for thesidelink transmission. At step 6 s, the second UE uses the resourceindicated in the resource allocation grant to transmit over the PC5interface. At step 6 u, the first UE relays the data to the base stationover the Uu interface. As discussed previously, the resource allocationgrant may be valid for an SC period. Therefore, as illustrated, in thenext SC period, the first and second UE repeat the scheduling requestsand transmission procedures in steps 7 to 10 u.

FIG. 9 is a message flow diagram illustrating an example resourceallocation process 900 for a UE that operates in network scheduled modeaccording to the technique described in FIG. 3 and associateddescription. In the illustrated example, the first UE may requestsidelink scheduled resources from the network.

In some cases, the requested resources may indicate the aggregatedsidelink data traffic generated by the first and the second UE(s). Inthese or other cases, the first UE may indicate the size of theaggregated data to a base station in a sidelink BSR. In some cases,multiple uplink or downlink data flows may be served by a first UE forthe same group in a given SC period. In these or other cases, the firstUE may then share the granted resources among the different flows.

In some cases, the first UE may indicate resource requests for eachindividual sidelink traffic flow to the network by transmitting buffersize information associated with each logical channel group (LCG) in thesidelink BSR. For example, the transmissions from a relay UE to multipleremote UEs may be mapped to one LCG, and the transmissions from eachremote UE to the relay UE may be mapped to a respective LCG. In somecases, the mapping may reflect the relative priorities of thesedifferent traffic flows. For instance, the transmissions from the relayto the remote UEs may be mapped to a higher priority LCG, while thetraffic from the remote UEs to the relay may be mapped to a lowerpriority LCG In these or other examples, the relay UE may calculate thebuffer size for each LCG independently and populate the sidelink BSRwith the calculated buffer size for each LCG

In some cases, a base station operating in a Frequency DivisionMultiplex (FDD) mode may avoid scheduling uplink Uu transmissions, orreduce the number of uplink Uu transmissions and retransmissions, in thesubframes allocated for sidelink transmissions. This approach may reducecollisions of the sidelink transmission with other uplink transmissionsin the coverage area of the base station. Similarly, a base stationoperating in a Time Division Multiplex (TDD) may avoid scheduling uplinkand downlink Uu transmissions or reduce the number of Uu transmissionsin the subframes allocated for sidelink transmissions to reducecollisions.

The process 900 may begin at step 1, where the first UE is configuredfor D2D transmissions. At step 2, the first UE receives a SystemInformation Block (SIB) message from the base station. At step 3, thefirst UE enters into RRC_CONNECTED state. At step 4, the first UEtransmits sidelink UE information to the base station. At step 5, thefirst UE receives an RRC connection reconfiguration message from thebase station. In some cases, the first UE may transition to the RRC_IDLEstate. At step 6 s, the first UE receives a resource allocation requestfrom the second UE. In some cases, the first UE may have entered theRRC_CONNECTED state in advance of receiving the resource allocationrequest. In some cases, the resource allocation request may trigger thefirst UE to transition into the RRC_CONNECTED state.

At step 6 u, the first UE sends a sidelink resource request to the basestation. In some cases, the sidelink resource request may be a resourcerequest for D2D transmission. In some cases, the sidelink resourcerequest may be a scheduling request. In some cases, the sidelinkresource request may be a BSR. As discussed previously, in some cases,the sidelink BSR may include the buffer size of the sidelink resourcesrequired by the second UE. Alternatively or in combination, the sidelinkBSR may include aggregated buffer size of the sidelink resourcesrequired by multiple UEs. At step 7 u, the base station sends thesidelink allocation information to the first UE. In some cases, thesidelink allocation information may be a sidelink resource grant. Insome cases, the sidelink allocation information may be a resourceallocation for D2D transmission. In some cases, the sidelink allocationinformation is transmitted using a DCI format 5 or an enhanced DCIformat over a Physical Downlink Control Channel (PDCCH) or an enhancedPDCCH (EPDCCH). At step 7 s, the first UE sends a resource allocationgrant to the second UE. The resource allocation grant indicates theresource for the sidelink transmission based on the sidelink allocationinformation received from the base station at step 7 u. At step 8 s, thesecond UE uses the resource indicated in the resource allocation grantto transmit over the PC5 interface. At step 8 u, the first UE relays thedata to the base station over the Uu interface.

As discussed previously, the sidelink allocation information may bevalid for an SC period. Therefore, as illustrated, in the next SCperiod, the resource allocation procedures are repeated in steps 9 s to11 u.

In some cases, the first UE may transmit the related pool information tothe second UE at the start of the direct communication session. In somecases, the first UE may transmit the pool information, e.g.,commTxPoolExceptional, to the second UE when an exceptional case occursor in advance to such an event. In some cases, the same techniques as(or techniques similar to) the techniques described previously to signalpools to be used in normal condition can be used.

In some cases, the overhead associated with the resource requests andresource grants may be minimized to reduce overheads. In one example,the base station may configure a transmission pool specific for sidelinktransmissions between a first UE and other UEs connected to the first UEover a PC5 interface or a sidelink transmission link. In some cases, thefirst UE may be a relay UE and the other UEs are one or more remote UEs.The Configuration information of this pool may be communicated to thefirst UE in an RRCConnectionReconfiguration message or other RRCmessages. The resources of a single pool may be shared between the firstUEs and other UE(s) for their sidelink transmissions. The base stationmay avoid scheduling Uu transmissions in the subframes allocated in thispool. For example, the base station in LTE FDD operation may avoidscheduling uplink transmissions or reduce the number of uplinktransmissions and retransmissions in the subframes in the transmissionpool in order to reduce probability of collisions between uplink(re)transmissions and sidelink transmissions below a certain level incase the uplink and the sidelink transmissions use the same frequency orcause interference to each other. The eNB in LTE TDD operation may avoidscheduling uplink and downlink transmissions or reduce the number ofuplink and downlink transmissions and retransmissions in the subframesin the transmission pool in order to reduce the probability ofcollisions between uplink and downlink (re)transmissions and sidelinktransmissions below a certain level in case the uplink, downlink and thesidelink transmissions use the same frequency or cause interference toeach other. The first UE may split the resource pool in two or moresubsets, a first subset to be used by the first UE and a second or moresubsets to be used by other UEs. The first UE may indicate theconfiguration information of the second or more subsets of sidelinkresources (SCI and data resources) to the other UEs. For example,considering a first UE and a second UE operating in autonomous selectionmode, the first UE and the second UE may each select a subframe for SCItransmission randomly from the configured SC pool. If both UEs share aSC pool consisting of 8 subframes and have data to transmit in a next SCperiod, the probability of collision is 8/(8*8)=⅛ which is significantlyhigh and may disrupt subsequent data transmissions in the SC period. Ifthe first UE and the second UEs are configured with non-overlapping SCpool subsets, the collision probability is reduced to zero.Alternatively, the two subsets may overlap in certain amount to keep thecollision probability below a certain level. For example, if 2 out of 8subframes overlap then the collision probability is 2/64=1/32. Pleasenote that use of subsets of configured resource pool can be alsoapplicable to data pool to avoid or reduce probability of collisions.Alternatively or in combination, the base station may configure two ormore subsets of sidelink transmission resources: the first subset forthe first UE and the second or more subsets for the other UEs. The basestation may indicate the configuration information of these subsets oftransmission resources to the first UE and the first UE may configurethe other UEs to use the second or more subsets. In these or otherexamples, the other UEs may select a resource in the second subset toperform a D2D transmission without sending a resource request andwaiting for a resource grant.

In some cases, the traffic characteristics of the sidelink transmissionsmay be semi-static, e.g., in a voice communication. In these or othercases, the resource grants discussed previously may be transmitted in areduced format to reduce overheads. In some cases, a resource pool maybe preconfigured at the second UE. In these or other cases, the first UEmay not send configuration information of a resource pool to the secondUE. Furthermore, the first UE may send the resource grant in a reducedformat. For example, the resource grant may include only a time resourcepattern. The second UE can determine the sidelink resource for D2Dtransmissions by the second UE in the preconfigured pool based on thetime resource pattern received from the first UE.

In some cases, one or more time resource patterns may be semi-staticallyconfigured. For example, a second UE may store one or more preconfiguredtime resource patterns. In some cases, different patterns may beconfigured in different UEs of the same group to reduce potentialcollisions. In some cases, the patterns may be configured based on theservice type or QoS information associated to the D2D transmission atthe second UE. In these or other cases, the second UE may use thepreconfigured time resource patterns without receiving the patterns fromthe first UE.

In some cases, the second UE may select a resource to transmit sidelinktransmissions in a preconfigured pool without sending a request forsidelink resource to the first UE, but the first UE may be able tocontrol the resource selection by the second UE. In these or othercases, the first UE may control or overwrite the preconfigured poolconfiguration information. In these or other cases, the first UE maysend a resource grant in a reduced format. The resource grant mayinclude a time resource pattern, an SC period, a subframe bitmap, or apool offset to be used by the second UE to reduce collisions.

In some cases, the second UE may signal to the first UE the relevantinformation on its preconfigured transmission pool. The first UE maytake this information into account when scheduling its transmissions toreduce collisions, e.g., on the PC5 interface and between the PC5 andthe Uu interfaces. The preconfigured sidelink transmission resource poolinformation used by the second UE may be further shared with the basestation for coordinating resource usage between the base station, thefirst UE, and other UEs.

In some cases, an extended period may be used for sidelink resourceallocation. The extended period may be used to extend the validity of aresource allocation beyond an SC period. Extending the validity of thesidelink resource allocation may reduce signaling overhead, inparticular for conversational bearer types, e.g., bearers for voicecommunication, because the associated transmission resources needs aretypically uniform and easy to predict.

In some cases, the extended period may be used for either direction of asidelink transmission between a first UE and a second UE. In some cases,the extended period may be used when the first UE operates in either theautonomous selection mode or the network scheduled mode. In some cases,the extended allocation period may be used in combination to thetechniques described in FIG. 2-3 and associated descriptions, or incombination with other techniques described in the present disclosure.In some cases, the extended period may be used for downlink datareceived at the first UE from the network via an Evolved Packet System(EPS) unicast bearer, a Multicast Broadcast (MBMS) multicast bearer, ora Single Cell Point-to-Multipoint (SC-PTM) multicast bearer. In somecases, the first UE may be a relay UE, while the second or other UEs maybe remote UEs.

In some cases, whether the extended period may be used may depend onseveral factors. The factors may include the QoS information. Forexample, the extended period may be used if QCI is set to 65, whichindicates an MCPTT voice service. The factors may also include theduration of the configured SC period. For example, if the SC period isset to a short period, e.g., 40 or 80 ms, then extended period may beused. The factors may also include the expected duration of a signalingprocedure or of a sequence of signaling procedures. For example, if a UEis attempting to establish a Network Mode Operation via Relay (NMO-R)for an MCPTT direct communication session, the signaling procedure maytake longer than the SC period and the extended period may be used.

In some cases, a second UE may request resources to a first UE, a firstUE may grant resources to the second UE, a first UE may requestresources to a base station, and/or a base station may scheduleresources for a first or a second UE. In some cases, at least one of afirst UE, a second UE, or a base station may indicate a capability tosupport the extended period. For example, a second UE may indicate itssupport of the extended period to the first UE. This capability may beprovided during the connection establishment phase to the first UE ormay be indicated implicitly or explicitly in the resource request. Thefirst UE may indicate its support of the extended period to the secondUE in a resource allocation configuration. The first UE may alsoindicate its capability to the base station explicitly or implicitly inan extended or enhanced sidelink BSR. The base station may indicate itssupport of the extended period using an indication in an SIB, forexample a SIB Type 18. Alternatively, this capability may be indicatedin point-to-point RRC messages involved in D2D communicationsprocedures, e.g., an RRC Connection Reconfiguration message.

In some cases, a single capability indicator may be used. In some cases,different capability indicators may be used for reception andtransmission, respectively.

In some cases, techniques ensuring the compatibility between anequipment supporting an extended period and another equipment notsupporting or not using an extended period may be operated. For example,if a UE sends a request for an extended resource allocation period andreceives a non-extended grant, the UE may interpret that the extendedperiod is not used.

In some cases, a second UE may include an explicit indication for theextended period in a resource request. Alternatively or in combination,a request for the extended period may be transmitted implicitly as partof the QoS information in the resource request.

In some cases, the duration of the extended resource allocation periodmay be signaled explicitly, e.g., as an absolute period of time, or as amultiple of the configured SC period. Alternatively or in combination,the extended resource period may be an undetermined duration. Forexample, the extended period may persist until an indication isreceived. In some cases, the indication may be a “stop” indication. Insome cases, the indication may be an indication that the extendedresource allocation becomes invalid.

In some cases, the duration indication of the extended resourceallocation period may be indicated in an enhanced SCI format 0 over aPSCCH, or in a dedicated point-to-point signaling message over a PSSCH.In some cases, the first UE, e.g., a relay UE, may multicast theduration indication in the MIB-SL message on a PSBCH. In some cases, oneor more default duration values may be specified, e.g., in a 3GPPstandard. In some cases, the default duration values may be associatedto types of bearers, e.g., voice or PTT bearer types, or related QoSinformation.

In some cases, the extended resource allocation period may start uponreception of an extended resource allocation period indication in anenhanced SCI format 0 or point-to-point signaling message. In somecases, the extended resource allocation period may start implicitly ifthe associated bearer type is activated. In some cases, an extendedresource allocation period may start upon the reception of an indicationin an enhanced SCI format 0 over a PSCCH or in a dedicatedpoint-to-point signaling message. In some cases, the indication may be a“start” indication. In some cases, the indication may be an indicationthat an extended resource allocation becomes valid. In some cases, anextended resource allocation period may end upon the reception of anindication in an enhanced SCI format 0 over a PSCCH or in a dedicatedpoint-to-point signaling message. In some cases, the indication may be a“stop” indication. In some cases, the indication may be an indicationthat the extended resource allocation becomes invalid. The “stop”indication, or the indication that the extended resource allocationbecomes invalid, may be used when the extended period has startedimplicitly, e.g. associated to a type of bearer, or explicitly, e.g.,upon reception of a duration indication or of a “start” indication.

In some cases, an extended resource allocation period may startimmediately upon reception of an indication, e.g., a duration indicationor a “start” indication. Alternatively or in combination, an extendedresource allocation period may start at a specific time, e.g., at thebeginning of the next SC period.

In some cases, the extended resource allocation period may end upon theexpiry of an inactivity timer or upon a reconfiguration of thetransmission pool. The inactivity timer may be started when no data isavailable for sending at the transmitter or no data is received in theassigned resources at the receiver. When the inactivity timer expires,the corresponding resource may be implicitly considered as invalid orreleased for the concerned session and can be reallocated to anothersession.

In some cases, a request for an extended resource allocation or for anextended configured grant may be provided to the base station through anextended resource allocation request indicator in an enhanced BSR, atime period duration indication, or a combination thereof. The absenceof a time period duration in the request from the first UE may signifythat the network should determine the extended period, that the periodduration is a default value possibly associated to a given bearer typeor QoS, or that the extended period should be indefinite.

In reply, the base station may grant the requested resource for anextended period of time. The granted period may be period indicated bythe first UE in the request to the base station, a different perioddetermined by the base station, or an indefinite period.

In some cases, the base station may be aware that the first UE supportsthe extended resource allocation technique, e.g., via UE capability. Inthis case, the network may determine and allocate resources with anextended validity time period without receiving a request for anextended period. In some cases, the decision to grant the extendedperiod may be based on QoS information associated to the requestedresource.

The base station may signal to the first UE the extended resourceallocation using an enhanced DCI format 5 over PDCCH or EPDCCH over theUu interface.

The first UE may further request the release of the extended resourceallocation, e.g., at the end of a talk burst from a second UE. In somecases, the extended resource allocation may be released when therequested, the granted or the default extended period duration expires.Alternatively, the network may explicitly terminate the extendedresource allocation period using a normal or enhanced DCI format 5 or aRRC message.

In some cases, the end of the extended resource allocation period may beconditioned by an inactivity timer. The timer may be started when nodata is available for sending at the transmitter or no data is receivedin the assigned resources at the receiver. When the inactivity timerexpires, the corresponding resource may be implicitly considered asreleased for the concerned session and can be reallocated for anothersession.

FIG. 10 is a message flow diagram illustrating an example extendedresource allocation period process 1000 for a remote UE operating in theautonomous selection mode. In the illustrated example, the extendedperiod is initiated by a “start” indication and terminated based on aninactivity timer at the relay UE. The process 1000 begins at step 1,where the base station indicates that the autonomous selection mode isused for sidelink transmission. At step 2, the remote UE discovers andselects the relay UE for D2D transmission. At step 3, the relay UEtransmits the extended resource allocation capability, which indicatesthe support of the extended resource allocation period technique. Atstep 4, the remote UE selects a resource for the sidelink transmissionand determines to use extended allocation for the selected resource. Insome cases, the remote UE determines to apply the extended resourceallocation period based on the QoS information associated with thebearer type of the sidelink transmission. At step 5, the remote UEtransmits a “start” indication, which indicates that it will useextended resource allocation. At step 6 s, the remote UE transmits onthe PC5 interface using the resources allocated for an extended periodthat extends beyond an SC period. At step 6 u, relay UE relays thetransmission to the base station. At step 7, the remote UE completes thetransmission and stops sending data. This triggers the inactivity timerat the relay UE. At step 8, the timer expires, and the relay UEdetermines that the extended resource is released.

FIG. 11 is a message flow diagram illustrating an example extendedresource allocation period process 1100 for a relay UE operating in theautonomous selection mode and scheduling resource allocation for remoteUEs according to the technique described in FIG. 2 and associateddescription. In the illustrated example, the extended period isconfigured by the relay UE. The process 1100 begins at step 1, where thebase station indicates that the autonomous selection mode is used forsidelink transmission. At step 2, the remote UE discovers and selectsthe relay UE for D2D transmission. At step 3, the relay UE transmits theextended resource allocation capability, which indicates the support ofthe extended resource allocation period technique. At step 4, the remoteUE transmits a resource request to the relay UE. At step 5, the relay UEselects a resource for the sidelink transmission and determines to useextended allocation for the selected resource. In some cases, the relayUE determines to apply the extended resource allocation period based onan explicit indication in the resource request. Alternatively or incombination, the relay UE determines to apply the extended resourceallocation period based on the QoS information in the request. At step6, the relay UE transmits an extended resource allocation. The extendedresource allocation includes a configured duration for which theresource allocation is valid. At step 7 s, the remote UE transmits onthe PC5 interface using the resources allocated for an extended periodthat extends beyond an SC period. At step 7 u, the relay UE relays thetransmission to the base station. At step 8, the extended period ends,and the allocated resource is no longer valid.

FIG. 12 is a message flow diagram illustrating an example extendedresource allocation period process 1200 for a relay UE operating in thenetwork scheduled mode and scheduling resource allocation for remote UEsaccording to the technique described in FIG. 3 and associateddescription. In the illustrated example, the extended period isinitiated by a “start” indication and terminated by a “stop” indication.The process 1200 begins at step 1, where the relay UE operates inRRC_IDLE mode. At step 2, the relay UE receives SIB 18 from the basestation. At step 3, the relay UE enters into RRC_CONNECTED state withthe base station. At step 4 a, the relay UE transmits the extendedresource allocation capability, which indicates the support of theextended resource allocation period technique. At step 4 b, the relay UEtransmits sidelink UE information to the base station. At step 5, thebase station transmits an RRC connection reconfiguration message to therelay UE.

At step 6, the remote UE transmits an extended resource request to therelay UE. At step 7, the relay UE determines to use extended allocationfor the requested resource. In some cases, the relay UE determines toapply the extended resource allocation period based on an explicitindication in the resource request. Alternatively or in combination, therelay UE determines to apply the extended resource allocation periodbased on the QoS information in the request. At step 8, the relay UEtransmits an enhanced sidelink BSR, an extended resource allocationrequest, or a combination thereof to the base station to indicate arequest for extended resource allocation. At step 9, the base stationgrants the extended resource and indicates the resource over a PDCCH oran EPDCCH using an enhanced DCI format 5. At step 10, the relay UEtransmits an extended resource allocation. The extended resourceallocation includes a “start” indication for an extended period. At step11 s, the remote UE transmits on the PC5 interface using the resourcesallocated for an extended period that extends beyond an SC period. Atstep 11 u, the relay UE relays the transmission to the base station. Atstep 12, the remote UE stops the transmitting. At step 13, the networkdetects end of data transmission based on the expiration of aninactivity timer. At step 14, the base station transmits a “stop”indication to indicate that the extended period has ended. At step 15,the relay UE transmits a “stop” indication to indicate that the extendedhas ended and the allocated resource is no longer valid.

In some cases, the sidelink transmission over the PC5 interface and theuplink or downlink transmission over the Uu interface may be coordinatedto reduce interferences. For example, in a downlink voice traffic, therelay UE may receive a Radio Link Control (RLC) Unacknowledged Mode Data(UMD) Protocol Data Unit (PDU) every 20 milliseconds for regular voiceframes or 40 milliseconds for bundled voice frames from the basestation. In some cases, the relay UE may determine that the downlinkPDUs arrival is periodical with a limited range of jitter based onperiodicity of data or on a semi-persistent scheduling (SPS)configuration. The relay UE may select a TRP for sidelink transmissionfrom the second UE that minimizes the latency at the relay UE. Theselection of the TRP may also take into account the structure of theresource pool and the processing delay needed for the relay to forwardthe frames between the Uu and the PC5 interfaces.

The relay UE may signal to the remote UE the selected TRP via SCI format0. The relay UE may also determine that the selected TRP can be used foran extended resource allocation period and indicate the TRP in anextended sidelink resource grant via an extended SCI format 0.

Similarly, the base station may determine that the arrival of downlinkpackets destined to the relevant group is periodical with a limitedrange of jitter. The base station may select an appropriate TRP for thesidelink transmissions from the relay and signal sidelink resourceassignment over the Uu interface accordingly via DCI format 5. Theselection of the TRP may take into account the scheduling timing of thedownlink RLC PDUs over the Uu interface and the processing time of therelay UE, e.g., receiving and decoding downlink transport blocks andtransmitting them over sidelink, for minimizing the latency at the relayUE. The base station may determine that the selected TRP can be used foran extended resource allocation period and indicate the TRP in extendedsidelink resource grant via an extended DCI format 5.

In some cases, the relay UE may determine the timing for transmittingScheduling Request (SR) and/or Buffer Status Report (BSR) on the Uuinterface for Uu uplink resource allocation based on the controlinformation or data received on the PC5 interface. FIG. 13 is a messageflow diagram illustrating an example SR transmission process 1300 for arelay UE operating in the autonomous selection mode. In some cases, therelay UE may transmit an SR at preconfigured SR instances. Thepreconfigured SR instances may occur at the beginning of each SR period.

The process 1300 may begin at 1302, where an SCI is received at therelay UE from the remote UE. Because the SCI indicates information for apending sidelink data transmission, the relay UE may determine that therelay UE is likely to receive a data packet from the remote UE.Therefore, it is likely that the relay UE may need to request an uplinkresource from the base station by sending an SR and then eventuallysending a BSR. In some cases, the relay UE may transmit the SR at thefirst available SR opportunity or SR instance after receiving an SCI.This approach may minimize the delay between possible reception of oneor more PDUs on the sidelink and the subsequent transmission of the oneor more PDUs to the base station on the uplink and, therefore, may beuseful for high delay-sensitive applications.

Subsequent to the transmission of SR, the relay UE sends a BSR to thebase station to indicate the pending data in the relay UE's uplinkbuffer. The relay UE may estimate the amount of data based on thecontent of the SCI format 0 received from the remote UE, e.g., averagenumber of subframes scheduled for transmission on the PSSCH, resultingallocated bandwidth, or modulation scheme. Upon receiving a BSR, in somecases, the base station may grant the uplink resource before the relayUE successfully decodes the PDU from the remote UE. In this case, therelay UE may send an additional BSR in the granted resource to indicatethat the PDU has not yet been successfully decoded.

At 1304, the relay UE may receive a first redundancy version of thefirst PDU from the remote UE. In some cases, the remote UE may transmita data packet to the relay UE using more than one redundancy versions.Each time the relay UE receives a redundancy version, the relay UE maycombine it with previously received redundancy versions and attempt todecode the combined versions. In some cases, the relay UE may transmitthe SR at the first SR instance after receiving a redundancy version ofthe data packet. This approach delays the SR slightly compared to theoption where the UE sends the SR after receiving the SCI as describedpreviously, but increases the likelihood that the PDU on the PC5 willhave been successfully decoded prior to the uplink grant on the Uuinterface. The relay UE may also send a BSR to the base station toindicate the buffer size. As discussed previously, if the uplink grantarrives before successful decoding of the PDU, the relay UE may indicateto the base station that there is further data to come in uplink byincluding another BSR in the granted resource.

At 1306, the relay UE successfully decodes at least one of the one ormore PDUs from the remote UE. In the illustrated example, this happenswhen the second redundancy version of the PDU is received. In this case,the relay UE may transmit the SR after the PDU is successfully decoded.In some cases, the relay UE may transmit the SR after the SC periodends. The UE may determine the size of received PDU and send BSR to thebase station accordingly. This latter approach eliminates the risk ofwasted uplink grants and may be useful for delay tolerant applications.

FIG. 14 is a message flow diagram illustrating an example SRtransmission process 1400 for a relay UE operating in the networkscheduled mode according to the technique described in FIG. 3 andassociated description. The process 1400 may begin at step 1, where therelay UE is configured for D2D transmissions. At step 2, the relay UEreceives a SIB message from the base station. At step 3, the relay UEenters into RRC_CONNECTED state. At step 4, the relay UE transmitssidelink UE information to the base station. At step 5, the relay UEreceives an RRC connection reconfiguration message from the basestation.

At step 6 a, the relay UE receives a resource allocation request fromthe second UE. At step 6 b, the relay UE sends a sidelink BSR to thebase station. In some cases, the relay UE may send an uplink BSR foruplink resource request on the Uu interface. Requesting Uu uplinkresources before receiving the SCI may further reduce the delays. Atstep 7 a, the base station sends the sidelink allocation information tothe first UE. At step 7 b, the first UE sends a resource allocationgrant to the second UE. As discussed previously, the UE may transmit anSR at step 8 a, which is the first SR instance after receiving the SCI.The UE may also transmit an SR at step 8 b, which is the first SRinstance after receiving the first redundancy version of the PDU fromthe remote UE, or at step 8 c, which is the first SR instance aftersuccessfully decoding the PDU.

FIG. 15 is a flowchart illustrating an example method 1500 forallocating resources for D2D transmissions. The method 1500 may begin atblock 1502, where the first UE and the second UE are determined to bewithin D2D proximity. At least one of the first UE or the second UE isoutside of a network coverage. In some cases, determining the D2Dproximity includes discovery between the first UE and second UE.

At block 1504, a configuration of the D2D radio resources is determined.In some cases, the configuration of the D2D radio resources isdetermined to substantially reduce D2D transmission collisions betweenthe first UE and the second UE. In some cases, the determination is madeby a base station. In some cases, the determination is based on thepreconfigured D2D transmission resource within the second UE. In somecases, the determination is made by the first UE within the D2D radioresources configured by the base station.

At block 1506, a grant from the determined D2D radio resources for thetransmissions from the second UE to the first UE is assigned. In somecases, the grant is assigned by the first UE.

FIG. 16 is a flowchart illustrating another example method 1600 forallocating resources for D2D transmissions. The method 1600 may begin atblock 1602, where a resource allocation configuration is transmittedfrom a base station to a first UE for device-to-device transmission. Insome cases, the first UE operates in an autonomous allocation mode or anetwork scheduled mode.

At block 1604, the first UE determines a configuration of the resourcepool for the second UE within the resource pool configured by the basestation in such a way to avoid or substantially reduce simultaneoustransmissions between the first UE and the second UE, or collisions ofdevice-to-device transmissions between the first UE and the second UE.In some cases the second UE operates in autonomous selection mode. Atblock 1606, the first UE transmits to the second UE the resource poolconfiguration for the second UE

At block 1608, the second UE selects resource for the device-to-devicetransmission from the resource pool configured for the second UE andperforms transmission on the selected resource.

At block 1610, a device-to-device transmission is received from thesecond UE over the selected resource.

FIG. 17 is a flowchart illustrating an example method 1700 fortransmitting a scheduling request. The method 1700 may begin at block1702, where a sidelink control information is received at a relay UEfrom a remote UE. The relay UE is within a coverage area of a basestation. The remote UE is outside of the coverage area. The relay UE isconfigured to relay transmissions from the remote UE to the basestation. The sidelink control information indicates a futuretransmission of a data packet over a sidelink channel. In some cases,the remote UE operates in an autonomous selection mode. In some cases,the sidelink resource for the remote UE transmission is allocated by therelay UE or is scheduled by the network.

At block 1704, a scheduling request is transmitted to a base station. Insome cases, the scheduling request is transmitted to the base stationbefore transmission of the data packet. In some cases, the data packetis transmitted in more than one redundancy version, and the schedulingrequest is transmitted to the base station in response to receiving oneor more redundancy versions of the data packet. In some cases, thescheduling request is transmitted to the base station after the datapacket is decoded at the relay UE. In some cases, a buffer status reportthat indicates a buffer size associated with the scheduling request istransmitted to the base station.

At block 1706, a scheduling grant that indicates an uplink resource isreceived from the base station. At block 1708, a data packet over thesidelink channel is received from the remote UE. At block 1710, the datapacket is transmitted to the base station using the uplink resource.

FIG. 18 is a block diagram illustrating an example user equipment (UE)device 1800. The illustrated device 1800 includes a processing unit1802, a computer-readable storage medium 1804 (for example, ROM or flashmemory), a wireless communication subsystem 1806, a user interface 1808,and an I/O interface 1810.

The processing unit 1802 can include one or more processing components(alternatively referred to as “processors” or “central processing units”(CPUs)) configured to execute instructions related to one or more of theprocesses, steps, or actions described herein in connection with one ormore of the implementations disclosed herein. In some implementations,the processing unit 1802 may be configured to generate controlinformation, such as a measurement report, or respond to receivedinformation, such as control information from a network node. Theprocessing unit 1802 may also be configured to make a Radio ResourceManagement (RRM) decision such as cell selection/reselection informationor trigger a measurement report. The processing unit 1802 can alsoinclude other auxiliary components, such as random access memory (RAM)and read-only memory (ROM). The computer-readable storage medium 1804can store an operating system (OS) of the device 1800 and various othercomputer-executable instructions, logic or software programs forperforming one or more of the processes, steps, or actions describedabove.

The wireless communication subsystem 1806 may be configured to providewireless communication for voice, data, and/or control informationprovided by the processing unit 1802. The wireless communicationsubsystem 1806 can include, for example, one or more antennas, areceiver, a transmitter, a local oscillator, a mixer, and a digitalsignal processing (DSP) unit. In some implementations, the subsystem1806 can support multiple-input multiple-output (MIMO) transmissions. Insome implementations, the receiver in the wireless communicationsubsystems 1806 can be an advance receiver or a baseline receiver. Tworeceivers can be implemented with identical, similar, or differentreceiver processing algorithms.

The user interface 1808 can include, for example, one or more of ascreen or touch screen (for example, a liquid crystal display (LCD), alight emitting display (LED), an organic light emitting display (OLED),a micro-electromechanical system (MEMS) display), a keyboard or keypad,a trackball, a speaker, and a microphone. The I/O interface 1810 caninclude, for example, a universal serial bus (USB) interface. Variousother components can also be included in the device 1800. A number ofembodiments of the invention have been described. Nevertheless, it willbe understood that various modifications may be made. Accordingly, otherembodiments are within the scope of the following claims.

While operations are depicted in the drawings in a particular order,this should not be understood as requiring that such operations beperformed in the particular order shown or in sequential order, or thatall illustrated operations be performed, to achieve desirable results.In certain circumstances, multitasking and parallel processing may beemployed. Moreover, the separation of various system components in theimplementation descried above should not be understood as requiring suchseparation in all implementations, and it should be understood that thedescribed program components and systems can generally be integratedtogether in a signal software product or packaged into multiple softwareproducts.

Also, techniques, systems, subsystems, and methods described andillustrated in the various implementations as discrete or separate maybe combined or integrated with other systems, modules, techniques, ormethods. Other items shown or discussed as coupled or directly coupledor communicating with each other may be indirectly coupled orcommunicating through some interface, device, or intermediate component,whether electrically, mechanically, or otherwise. Other examples ofchanges, substitutions, and alterations are ascertainable by one skilledin the art and could be made.

While the above detailed description has shown, described, and pointedout the fundamental novel features of the disclosure as applied tovarious implementations, it will be understood that various omissions,substitutions, and changes in the form and details of the systemillustrated may be made by those skilled in the art. In addition, theorder of method steps are not implied by the order they appear in theclaims.

What is claimed is:
 1. A method for allocating radio resources between afirst user equipment (UE) and a second UE over a direct radiocommunication link, comprising: transmitting, by the first UE, a requestfor radio resources over the direct radio communication link; inresponse to the request for radio resources over the direct radiocommunication link, receiving, by the first UE, resource controlinformation indicating a radio resource allocation made by the secondUE, and using, by the first UE, the allocated radio resource to transmitdata over the direct radio communication link.
 2. The method of claim 1,wherein the direct radio communication link is a sidelink communicationlink.
 3. The method of claim 1, wherein the direct radio communicationlink is a PC5 communication link.
 4. The method of claim 1, furthercomprising: receiving, by the first UE, an indicator indicating that thesecond UE supports resources allocation over the direct radiocommunication link.
 5. The method of claim 4, wherein the first UEreceives the indicator from the second UE.
 6. The method of claim 1,further comprising: transmitting, by the first UE, an indicatorindicating that the first UE supports resources allocation over thedirect radio communication link.
 7. The method of claim 1, wherein theradio resources are allocated using a remote resource allocation.
 8. Themethod of claim 1, wherein the request for radio resources indicatesQuality of Service (QoS) information.
 9. The method of claim 1, whereinthe resource control information indicates a frequency resource or atime resource.
 10. The method of claim 1, wherein the resource controlinformation indicates an allocation period for the radio resourceallocation.
 11. The method of claim 10, wherein the allocation period isone of a nonextended resource allocation period or an extended resourceallocation period.
 12. The method of claim 11, wherein the extendedresource allocation period persists for a multiple of a configuredperiod.
 13. The method of claim 11, wherein the extended resourceallocation period persists until an indication indicating that theextended period ends is received.
 14. The method of claim 11, whereinthe extended resource allocation period persists until an indicatedduration expires.
 15. The method of claim 1, further comprising:receiving, by the first UE, a capability indicator indicating that thesecond UE supports an extended resource allocation period for the radioresource allocation.
 16. The method of claim 1, further comprising:transmitting, by the first UE, a capability indicator indicating thatthe first UE supports an extended resource allocation period for theradio resource allocation.
 17. The method of claim 1, wherein the secondUE is inside of a network coverage, and the first UE is outside of thenetwork coverage.
 18. The method of claim 1, wherein the resourcecontrol information is transmitted using an enhanced Sidelink ControlInformation (SCI) format.
 19. A first user equipment (UE), comprising:at least one hardware processor; and a non-transitory computer-readablestorage medium coupled to the at least one hardware processor andstoring programming instructions for execution by the at least onehardware processor, wherein the programming instructions, when executed,cause the first UE to perform operations comprising: transmitting, bythe first UE, a request for radio resources over a direct radiocommunication link; in response to the request for radio resources overthe direct radio communication link, receiving, by the first UE,resource control information indicating a radio resource allocation madeby a second UE, and using, by the first UE, the allocated radio resourceto transmit data over the direct radio communication link.
 20. Anon-transitory computer-readable medium storing instructions which, whenexecuted, cause a computing device to perform operations comprising:transmitting, by a first UE, a request for radio resources over a directradio communication link; in response to the request for radio resourcesover the direct radio communication link, receiving, by the first UE,resource control information indicating a radio resource allocation madeby a second UE, and using, by the first UE, the allocated radio resourceto transmit data over the direct radio communication link.